Populating Next Right Pointers in Each Node II

 1 /**
 2  * Definition for binary tree with next pointer.
 3  * struct TreeLinkNode {
 4  *  int val;
 5  *  TreeLinkNode *left, *right, *next;
 6  *  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     void connect(TreeLinkNode *root) {
12         TreeLinkNode* cur = root;
13         while(cur) {
14             TreeLinkNode* node = cur;
15             TreeLinkNode* last = NULL;
16             cur = NULL;
17             while(node) {
18                 TreeLinkNode* left = node->left;
19                 TreeLinkNode* right = node->right;
20                 if(left || right) {
21                     if(last) last->next = left ? left : right;
22                     if(left) left->next = right;
23                     if(!cur) cur = left ? left : right;
24                     last = right ? right : left;
25                 }
26                 node = node->next;
27             }
28         }
29     }
30 };